It is not uncommon today to provide services through the use of various types of prepaid accounts. For example, prepaid accounts are in prevalent use in telephony systems, such as in mobile networks or wireless networks. In such systems, a prepaid calling system may be implemented that controls a subscriber's making of calls such that the subscriber can only make calls up to the value that they have actually paid into a particular account. For example, if the subscriber has prepaid twenty dollars to a particular account, that subscriber may be enabled to make twenty dollars worth of calls using that account.
There are a variety of system configurations which may be utilized in providing prepaid calling. For example, a service node system may be utilized in providing prepaid calling services. A service node is a system that is installed in the network with telephony trunks attached thereto. The network is configured such that calls or phones identified as being prepaid calls or phones are routed through the service node for connection to the dialed party by the service node when the account information has been verified (this type of in and out calling through a service node is often referred to as a trombone call or connection). The service node may look at various call information, such as the calling party to retrieve the appropriate account detail and the dialed number to determine a rate for that call. The service node may then monitor the duration of the call, tracking the account balance. If the account balance reaches a predetermined threshold amount, such as reaching a zero balance, the service node may end the call, such as by disconnecting the parties.
Another example of a prepaid calling system may be deployed in an intelligent network (IN) system. Such a system configuration is similar to the service node discussed above, but does not utilize trombone connections to a service node. Instead, in an IN prepaid system the network switches control the call and are able to disconnect a call if an account balance reaches a predetermined threshold amount, such as when a zero balance is reached. Typically, the IN prepaid system will operate very similar to the service node above in determining a proper account to debit, analyzing the dialed number to determine a call rate, and setting a timer or monitoring the call to disconnect the call when the account reaches a particular threshold.
Although the above examples of prepaid systems may be implemented in either traditional land-line telephone networks or wireless telephone networks, one prepaid system heretofore found only in wireless telephone networks, such as the group special mobile (GSM) environment of Europe, is a secure identification module (SIM) based prepaid system. In a SIM-based prepaid system, the subscriber account balance or purse is stored on the SIM of the wireless handset. Accordingly, the control algorithms of the SIM could stop the handset from making a call when the balance on the SIM falls below a predetermined threshold, such as when the balance reaches zero. In operation, the SIM-based system determines the cost of a call that the subscriber is then attempting to setup using signaling from the network. The signaling used is called “advice of charge” and provides information to allow algorithms in the handset to determine the cost of the call and, therefore, the time which the call may be maintained using the current purse balance. These algorithms may operate to monitor the call and disconnect the call when the balance reaches a predetermined threshold.
Another prepaid system that has heretofore been implemented only in wireless telephone networks is a handset-based prepaid system. In the handset-based prepaid system the handset has call tariff information stored therein. Accordingly, the handset may control rating of the calls based on the tariff structure which is stored within the handset. This solution does not require functionality in the network to perform prepaid call accounting. Accordingly, handset-based prepaid systems may be network independent and, therefore, may be used on multiple networks and may even be allowed to roam internationally.
For the above prepaid systems to operate effectively, they must accurately account for the services provided and maintain an accurate account balance. However, the majority of these systems operate under the assumption that the system is working correctly and, therefore, that fraud is not occurring. But fraud can occur in each of these systems by different mechanisms. In the global market, the fraudsters identify and exploit system aspects which appear to be the weakest point in such systems at that point in time. Accordingly, the fraud that occurs tends to be different year to year.
In the SIM-based prepaid system, for example, proper operation relies upon provision of accurate advice of charge information from the network to inform the SIM algorithms of the proper rate a call should be accounted for costed. Accordingly, fraudsters recognized that if they could infiltrate the loop in between the advise of charge message coming from the network and arriving at the SIM, the fraudsters could change that data or otherwise corrupt the data such that the SIM algorithms, although operating properly, would not correctly account for the cost of the call. For example, the advice of charge information may be manipulated or usurped to provide artificially low tariff rates, such that the SIM algorithms would correctly bill based on the information that it was provided, but that the information was incorrect for the actual call being made.
The handset-based prepaid system is not reliant on any signaling or information provided from the network and, accordingly, fraud on such systems may be accomplished using techniques different than that described above. Handset-based prepaid systems typically have tariff information tables and/or an account balance stored in encrypted memory to prevent fraud by preventing unauthorized persons from deciphering and manipulating the data. Using such encrypted data, a fraudster would not be able to know which bit of memory contained what data and, therefore, would not know what bits need to changed to achieve a desired result. However, fraudsters discovered that, on certain hardware architectures, they could read the information being written from the microprocessor in the handset to the encrypted memory. For example, some handset embodiments write this data in a serial fashion which is relatively easy to monitor. Accordingly, the fraudsters could make an exact copy or snapshot in time of the contents of the encrypted data file and replay this data to reset the handset to its status at a previous point in time (e.g., at a point before an account balance was depleted). For example, a fraudster might refill or top up the handset account balance once and, as the memory was being written to reflect the refilled amount (e.g., twenty dollars), a copy of that encrypted data may be made through use of special hardware coupled to the phone. Accordingly, at times thereafter, such as when the handset is turned off and then back on, the encrypted memory may be reset with this snapshot of the refilled or topped up handset status. In operation, the handset will operate to correctly tariff calls that it makes. However, the account balance will never be fully depleted because of the fraudster's ability to reset the status of the phone.
Service node prepaid systems generally operate under the assumption that fraud is avoided because the system monitors the call. For example, based on the signaling information that the service node receives, such as the originating line identity to specify the account calling and the number being dialed (the B party number), a service node prepaid system will use its tariff tables to rate the call and will monitor the duration of the call to determine a charge for the call. However, such systems can be subject to fraud if, for example, a fraudster devises a mechanism or a configuration in the network such that if a certain code is dialed, the call will not be routed through the service node. In such a situation the service node is never made aware of the call and, therefore, is not provided the opportunity to control the call. Accordingly, although the service node or the prepaid system itself may not be aware that any calls are being made, and therefore provides no indication of fraud, calls which are not being accounted for are actually being made.
Additionally, it is also possible in a service node prepaid system for a fraudster to modify an account balance on the service node by fraudulent means, such as through unauthorized access to the accounts by computer “hacking” techniques. Therefore, although the service node prepaid system may be operating properly and accurately monitoring a call, the costs of the call may not in fact be properly paid for.
The IN prepaid system may experience fraud from techniques similar to those discussed above with respect to the service node prepaid system. For example, in the IN prepaid system triggers and flags are generally used to make sure that the IN prepaid system is informed about a call's status and allowing the system to control the call as a prepaid call. A fraudster may change settings in the network such that the IN prepaid system was not aware of the call and, although the prepaid system appears to be functioning properly, no fraud is evident. Additionally, a fraudster in an IN prepaid system might gain unauthorized access to, i.e., hack, the balances associated with accounts in order to cause particular accounts to reflect larger balances than have actually been paid for, therefore allowing fraud to occur.
Therefore, there is a need in the art for systems and methods for detecting fraud in prepaid accounts.
There is a further need in the art for fraud detection to be provided independently of the prepaid system in order to detect fraud occurring on an otherwise properly operating prepaid system.